Purification of gases



Patented Oct. 11, 1932 nnnnsrr Josnrn. Lusn,

FATE

OF LONDON, ENGLAND PURIFICATION or eases No Drawing; Application filed October 20, 1930, Serial No.490,097, and in Great Britain October .31;,192 &..

Recently there has been an increased de-. mand' for hydrogen dueto the catalytic processesfor the production. of synthetic ammonia, synthetic methanol and fatty oil hydro-.

5 genation which has led. to an increase in the production of hydrogen from coal. Hydrogen obtained from coal contains sulphur com pounds such as carbon bisulphide and carbon oxysulphide which have hitherto only been removed at considerable cost, and even then not always completely.

Further, industrialgases such as coal gas,

coke oven gas, carburetted watergas' and producer gasfare'all liableto contain thesesulphur'oompoundswhich for many purposes it may be desirable to remove. i

Or again it may be desired to remove such sulphur compounds from airas in ,vis'cose artificial silk works, rubber works and carbon bisulphide factories, or other factories of solvents may be used, as for example, hy-

employing carbon bisulphide.

The object of the present invention is to simplifythe method of freeingthese gases from such deleterious sulphur compounds andfor thispurpose'use is made of piperidine or its homologues, hereinafter referred tons piperidine, since piperidine can be made sufliciently economically for thepurposes here inafter describedby the process asset out in 30 my Patent Nof1, 519,035 and my pending ap plication for patent Serial No. 316,884 filed November 2nd, 1928. V

I have found that when for example, coal gas is passed through piperidine dissolved in a suitable solvent the carbon bisulphide:

and oxysulphide are almost completely re y h i r sulphide compounds with pip'eridinev so that.

moved;

I have found that the piperidine may also be used in the form of a compound which is 0 readily dissociable such as are its compounds with carbon dioxide.

, suitable solvent.

Alternatively, the piperidine may be added to the gas in the form .of vapour vwhere it combineswith the carbon bisulphide .oroxysulphide to produce crystalline compounds =0 J in known manner.

The carbon dioxide compounds may be used in the dry state or in suspension in a llquld or ln solution .:111 a' which may be removed-from thegas st'ream' p p I I used lns tead of or 1n con un ct1on w th 'am mo I have further found that the crystalline compounds produced bythe reaction between the piperidine or piperidine compounds" and carbon bisulphide or oxysulphide can be treated for, the recovery of both the piperidine and the carbon bisulphide or oxysulphide by submitting the compounds in the presence of water to the action of carbon dioxide under pressure when piperidine carbonate is formed carbon bisulphide or oxysulphide is set. free. Or alternatively, the compounds may, be decomposed by means of acid whereby the, carbon bisulphide and oxysulphide are set. free and the piperidine salt thereby producedmay be treated with alkali to regenerate the piperidine. r I

. When piperidine or its-compounds are used 111 solution or suspension the choice of liquid medium depends onthe characteristics of the gas to .be treated. In general, a wide range drocarbon oils including coal tar and mineral oils, monoand polyhydric alcohols and ketones. The solvents used should prefer.- ably be those of low volatility so that they are; not carried away in the purified gas'streamL Water itself may be used, but owing to its low solvent power for carbon bisulphide and/or carbon oxysulphide its use not so] the removal of the oarbonbisulphide and/or carbon oxysulphide from the gas stream. is less complete. w 1

. In certain cases, for example, when piperidine carbonate is used, it may be thought de-f' sirable to use Water as a solvent to increase its concentration. In such a case it is desirable to use an aqueous solution of piperi'dine car-,7 bonate in the presence of a'suitable'oil inn-j miscible with water which increases the; solu-Q bility of the carbon bisulphide and/ or carbdn 1 oxysulphide. The 'piperidine may also .be

the first'of the followingexamples, the proc ess can form part of one for recovery of benzol from coal gas. 1

Emample 1 and containing 10 grains per 100 cu. ft. of sulphur, present asQcarbon bisulphide and oxysulphide'is passed through one or more Washers or. scrubbers of 0 suitable design through which a solution of'piperidine or compound of piperidine with carbon dioxide in gas oil is'circulated in counter current to the'gas The oil should forpreference not contain more piperidine than will remain dissolved in the oil afterbeing converted to its carbon. dioxide compound; With wet' gas this will be not more than.1%, but if the gas should previously have-been dried, higher concentrations may be used without any sepabulkyof' the. dissolved solid is precipitated);

' carbon dioxide to convert the base to ration on carbonation. the dryfcompound formed from piperidine and carbon dioxide may be as highas 1015% in gas oil, but with the additionof water the The quantity of oil-tobe circulated is dependent on the concentration of the dissolved piperidine beingabout 3000 4000 galls. 'per .millioncu; it. of gas for a 1% solution.

1 To. recover the traces of piperidine vola tilized from the washers, the-purified gas is passed through one or 'more scrubbers in which piperidine-free gas oil,o'r cold water, or; dil te sulphuric acid is circulating whereby the piperidine present inthe state of vapour maybe completely removed." The oil leaving'thesystem is filt ered, as soon as is necessary, to remove. thepiperidine-carbon bisulphid-e compounds precipitated and" if recovery *ofib'enzol'is desired, the oil isthen distilled to remove'the b'enzol. The oil is then returnedfto the system after the addi'-' tion of fre s'h piperidine or compound ot piperidine :withcarbon dioxide to replace that removed by reaction with carbon bisulphide and/or oxysulphide or by volatiliza-' tion. .Alternatively, if sufficiently free from piperidine, the. filtered oil may first'be used to scrub the purified gas to free it from piperidine vola'tilized from the washers. The S0111 tion ofpiperidine in gas oil before being re turned toithe washers, can'first .be treated with carbon dioxide or with a gas containing carbon'gdioxide compound.

j The solid compounds of piperidinelwith ca'rbon 'bisulphid'e and oxysulphide removed- (The solubility of .tillation.

The remaining. solution of piperidine sulphate is treated with a solution of caustic r 'sode. of 20-30% strength in quantity suf- Coal gas, substantially freed from hydro gen sulphide, ammonia and tarry impurities ficient to neutralize all the sulphuric acid previously used, when two layers separate the upper layer consisting of a. piperidinewater solution and the lower layer of saturated sodium sulphate" solution. The piperidine water solution is separated and treated with solid granulated caustic soda which removes the water,'the caustic soda solution produced separating ass lower layer which canbe'removed and usedin the neutralization of the" piperidine'sulphate solution. V The dried piperidine is recovered for further use.- mz

Coal gas, substantially freed from hydrogen sulphide, ammonia and tarry impurities and containing 30-40 grains per lOO cu. ft. of sulphur presentascarbon bisulphide and oxysulphideis passed through severalwash ers or scrubbers of suitable design containing an intimate mixture ofone part by volume of a5( aqueous solution of piperidine carbonate with [two parts by volume of gas oil. 100-500 galls, of .the mixture of gas oil and piperidinecarbonate solution are required permillion cu. "ft. ofgas treated. Traces of, piperidine volatilized from the washers are removedby a further washingof the gas with Water or dilute sulphuric acid. The crystals-of the compounds of carbon hisulphide and carbon oxysulphide with piperidine are removed by filtration and treated in water suspension in an enamel lined autoclave with carbon dioxide under. a

pressure of 30-50 atmospheres. The. carbon disulphide set free forms a' lower layer which can be discharged from theautoclave under pressure into a second I pressure vessel '.in whlch 1t 1s washed wh1le still under pressure with a smallproportion of caustic alkali or" alkali carbonate just sufficient to remove'the dissolved carbon dioxide. Fromthe solution ofpiperidine carbonate remaining, the piperidine can readily. be recovered for re-use in the process. I f What I claim is': 1. A" process of freeing industrial gases of sulphur" compounds and carbon sulphides whichconsists in subjecting the gas to be purified to the action of piperidine-J 2. A process of freeing industrial gases "of sulphur compounds V and carbon sulphides;-

which consists in subjecting the gas to be purified to the action of the homologues of piperidine.

3. A process offreeing industrlal gases of sulphur compounds and carbon sulphides which consists in passing the gas to be purified through a solution of piperidine.

4. A process of freeing industrial gases of sulphur compounds and carbon sulphides which consists in passing the gas to be purified through a solution of the homologues of piperidine.

5. A process of freeing industrial gases of sulphur compounds and carbon sulphides which consists in adding piperidine in vapor form to the gas to be cleansed.

6. A process of freeing industrial gases of sulphur compounds and carbon sulphides which consists in treating the gas with piperidine carbonate instead of piperidine substantially as described.

7. A process of freeing industrial gases of sulphur compounds and carbon sulphides which consists in subjecting the gas to be purified to the action of piperidine compounds simultaneously with known processes of removing carbon monoxide and benzol from the gases.

8. A process of freeing industrial gases of sulphur compounds and carbon sulphides which consists in subjecting the gas to be purified to the action of piperidine, subsequently effecting the recovery on the one hand of. the piperidine and its homologues and on the other of the sulphur compounds by subjecting the same to the action of acids and finally treating the piperidine salts with alkali substantially as described.

In testimony whereof I affix my signature.

ERNEST JOSEPH LUSH. 

